Air purity and being able to consistently remove contaminants entrained in the air is extremely important, especially in supposedly sterile or hygienic environments, such as hospitals and kitchens. It is also beneficial having decontaminated air in doctors surgeries, and workplace environments making it more difficult for germs and disease to spread.
In addition to microbiological contaminants, chemical gases or vapours can present a serious hazard, either as a by-product of industrial processing or as a malicious attack through terrorism or chemical warfare.